Foam-containing pressure-sensitive adhesive tapes are widely used for mounting objects such as pictures on walls or plastic body side molding on automobiles. Such a tape typically consists of a polyurethane, polychloroprene or polyethylene foam carrying a layer of pressure-sensitive adhesive on each face. For other uses, the adhesive layer may cover only one face, e.g., a tape useful as a cushioning gasket for an automobile window.
As disclosed in Canadian Pat. No. 747,341 (Engdahl, Buchholtz) and U.S. Pat. No. 3,993,833 (Esmay), a mixture can be foamed against a pressure-sensitive adhesive layer or between a pair of such layers. Alternatively the mixture may be foamed against a temporary carrier member which has a low-adhesion surface, followed by laminating one or two adhesive layers to the foam.
U.S. Pat. No. 3,565,247 (Brochman) concerns a pressure-sensitive adhesive tape, the adhesive layer of which is a foam, thus affording the economy of creating a tape in a unitary process, as opposed to the need to form the pressure-sensitive layer(s) separately when making foam-backed tapes. To make a tape of the Brochman patent, a blowing agent and a nucleating-reinforcing agent such as fumed silica are blended into a solution of a pressure-sensitive adhesive. After this blend is coated on a backing, it is heated to a temperature high enough to evaporate the solvent but not high enough to decompose the blowing agent. After the solvent has been evaporated, the temperature is increased to that necessary to decompose the blowing agent to release a gas which forms minute, generally spheroidal bubbles or microcells throughout the dried pressure-sensitive adhesive layer. Voids comprise 25 to 85% of the cellular adhesive layer. The Brochman patent reports that the cellular adhesive layer typically shows less than 5 percent recovery after being compressed to half its original thickness, the microcells collapsing under local high pressure.